It seems like some dogs are bothered more by storms than other dogs. We had a little Peke mix who was absolutely terrified any time it started to thunder, or after a ballgame and they had fireworks. At the first sound of thunder, she would be barking at the back door if she was out in the back yard; and then usually hiding under the bed as soon as she came in. Sometimes , she just jumped in my lap and shivered while the storm passed over.
Chipper really doesn't care about thunderstorms, and unless if is one of those huge thunderclaps that seem to hit right on top of the house, he simply ignores them. Of course, he is always right beside me; so maybe he is already where he feels safe.
Dogs can slo learn from other dogs sometimes. My friend had a lab who was terrified of thunder, and then got a little Pom who was not bothered by storms at all. After she saw how afraid the lab was of the storms; soon the Pom was afraid as well.